Telephone-exchange system.



PATENTED JULY -23, 1907.

3. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 11,1905.

' 2 SHEETSSHEET 1.

PATENTED JULY 23, 1907.

E. E. CLEMENT.

. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 11,1905.

2 SHEETS-SHEET 2.

F11 mam 3] wow 14 012 EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OFCOLUMBIA.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented July 23, 1907.

Application filedllovemher 11. 1905. Serial No. 236.889.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States,residing at Washington, in the District of Columbia, have invented acertain new and useful Improvement in Telephone-Exchange Systems, ofwhich the following is a specification, reference being had therein tothe accompanying drawings.

My invention relates to telephone exchange systems, and has for itsobject the improvement of such systems in general, and of common batterysystems in particular.

Briefly stated, the invention comprises a system in which tlie normalsupply for signaling over lines is fur nished by a secondary battery,which maintains a constant potential across the central office ends ofall the lines. Connection terminals are provided in open multiples ofthe line, and signal devices are included therein between the connectionterminals and the battery. The operators cordcircuits are all bridged onto the main generator, through impedance coils, the direction of forcesin the generator being such that when a connection is made with a line,like poles of the generator will be opposed to like poles of thesecondary battery, whereby a balance of potentials is produced on thelinesignal, and the battery is kept constantly charged. Since thebattery is floated across the terminals of the generator during allconversations, the inequalities in electromotive force due to thecommuting of the generator current, are smoothed out and do notinterferewith conversation.

My invention is illustrated in the accompanying drawings, in whichFigure 1 is a diagram of a central station and two subscribers stations.Fig. 2 is a diagram of a modification.

In Fig. 1 of the drawings, XY are the two subscribers stations, and W isthe central oflice. I have shown at each subscribers station the usualtransmitter T, receiver 1t, switch-hook and ringer, and instead of acondenser in series with each ringer I have shown a coherer, inaccordance with the design set forth in my Patents, 719,998 and 719,999v

At station X the transmitter is connected directly to the line-wire 2through the branch 9, on one side, and on the other side through theprimary '5 of the induction coil I and by wire 8 to the up-contact S ofthe switchhook S The secondary i of the induction coil is connected tothe receiver R. The switch-hook is connected to the line-wire l, and theringer Q is connected in a bridge 56-7 through the coherer G. Thiscoherer as shown is a glass tube mounted and insulated from theswitch-hook, with a filling of active material composed of a mixture offine hard carbon or very hard steel filings or broken needles or thelike.

At station Y, the transmitter and receiver are shown connected in seriesbetween the line-wire 3, through branch 10 to the contact s, theinduction coil being omitted. A coherer C is employed in series with theringer Q, in the bridge l314, but instead of being mounted on theswitch-hook, this coherer is fixed and is adapted to be tapped by ahammer h actuated by a cam stud on the hook lever S when the latterrises. The coherer and ringer are cut off during conversation by theopening of the bridge 121314 at the contacts.

At the central office, the lines are provided with contacts J, J, eachhaving a spring and sleeve j, j, bridged in open multiple. Pairs ofplugs, P, P are employed for interconnecting lines, their tips p andsleeves p being connected respectively through the cord-conductors 1820and 1719. A key K when actuated serves to connect ope-rators set 0through the wires 2122 across the cord conductors 1718. A ringing key Kwhen actuated, serves to separate the conductors 192O leading to thecalling-plug P, from those, l718 leading to the answering-plug P, and toput them on the Wires 2324 leading to the ringing generator G. Ipreferably include a condenser Z in the circuit of this ringinggenerator, because of the added effect thereby produced upon thecohere'rs.

The cordconductors 17l8 are permanently bridged on the main generator G,which has an output ample for the entire exchange load at all times, inorder to obviate any danger of overflow from the battery B.-

Between the generator and the cord-conductors I include the impedancecoils g, which are preferably of very low ohmic resistance, but so woundand with magnetic circuits so designed, that each will have a very highcoefiicient of self-induction. These coils serve the double purpose ofchoking out voice currents from the generator mains, and of smoothingout inequalities in the generator current conveyed to line. Asimilarfunction is performed. in each line by the coils L, L, the former ofwhich is the coil of the line-signal.

The operation of the system shown in Fig. 1 is as follows: Normallythere is no current flow in the lines, a though the battery B maintainsa constant potential difference between the terminals. When asubscriber, as X, calls he takes down his receiver, the hook rises, andline-signal L is energized by the current flow from battery B. Theoperator inserts the answering-plug P, and thereby connects thegenerator G across the line through the conductor 1718, in parallel withthe battery B. The signal L is thus exposed to equal potentials on bothsides, and the fiow of current through it from the battery stops. It isto be observed that the battery B is kept charged to its point ofhighest efi"1- ciency all the time, because the instant its potentialfalls, and an operator is answering a call anywhere in the office, thegenerator G will be connected back to it, and will charge it to themaximum. The generator supplies current to the line for talking, but thebattery is in parallel with it, and in conjunction with the coils gsmooths out the inequalities. After ascertaining the number wanted,through manipulation of the key K, the operator inserts plug P, andactuates ringing key K in the usual way. The sharp alternations ofcurrent thus produced on the line 3- cause the coherer C to set, anditsresistance to drop from its normal point of 140,000 ohms or more toless than 100 ohms, whereupon the ringer Q will be eHiciently actuated.When the subscriber Y answers the tapper h is raised and falls upon thecoherer to shake. apart its particles.

Fig. 2 is a diagram of a modified arrangement in which the magnets L andL are relays, and their associated magnets L and L may be relays, whilethe coils g already described are also the windings of relays whichcontrol the signals and are duplicated, the cord conductors being brokenby condensers, so as to give double supervision in a well known manner.

The substation apparatus is the same as in Fig. 1 except that I havesubstituted condensers for the coherers in the ringer branches, thisbeing a common and well known arrangement. Other changes can be madewithout departing from the invention.

Obviously, it the voltage of the battery B has fallen at any time, sothat there is a back flow of charging current through the magnet L, thesignal may remain actu ated unless special means are provided for itsretirement. To avoid this liability I prefer to make the magnet Lpolarized, as indicated in Fig. 2 and in that event it is sure to beproperly restored when a plug is inserted, for there is always sure tobe a small fractional difference of potential between the generator andthe battery terminals.

Having thus described my invention, what I claim is:

1. In a telephone system, a line circuit, a secondary battery supply,and controlling means for current in the circuit. a translating devicebetween the controlling means and the battery, a charging generator, andmeans to conncct the same during conversation between the controllingmeans and the translating device, substantially as described.

2. In an electrical system, a line circuit, a secondary battery forsupplying current thereto, a circuit closer, a connection terminal andmeans associated therewith to connect it with other circuits fortransmission purposes, said terminal being located between the circuitcloser and the signal device, and a charging generator adapted to beconnected to said connection terminal by the act of connecting it withanother circuit, substantially as described.

3. In a telephone exchange system, a subscribers metallic line circuit,a substation and switch, a storage battery and a line signal device witha permanent central oflice connection from the line through the signaldevice to the battery, a connection terminal for the line between thesubstation and the signal device, a coiiperating connective circuit forconnecting the line with other circuits, and a charging generatorbridged across the same so as to be brought into parallel with thestorage battery. and to produce a balance of potential across theterminals of the signal device while the line circuit is connected, andto recharge the battery through the signal device at such time whilemaintaining the signal inoperative, substantially as described.

4. In a telephone exchange system, a storage battery, a plurality ofsubscribers lines and signal controlling magnets therefor, each lineterminally connected at a central oflice through its signal magnet tosaid storage battery, subscribers station apparatus including telephonesand switches, a spring-jack or jacks for each line constituting openmultiples thereof outside of the signal controlling magnet, operatorsplugs and cord circuits, and a common charging generator connected inparallel across said cord circuits, whereby the subscribers will besupplied with talking current through the cord circuits, the signalcontrolling magnets will be deenergized, and the common storage batterywill be maintained fully charged, all substan tially as described.

In testimony whereof I have atfixed my signature in presence of twowitnesses.

EDWARD E. CLEMENT.

Witnesses HUGH M. STERLING, J. L. Warorrr.

